This invention concerns an apparatus for quenching filaments by directing and distributing the cooling gas entering the quenching area.
In a melt spinning process, filaments are extruded into a quenching chamber where heat is removed from the filaments typically by passing cooling gas, typically air, around the filaments. Makers of synthetic filaments are continually attempting to increase the speeds of their spinning processes and thus the quantity of polymer spun per unit time and also the uniformity of their products. However, melt spinning processes are limited by the rate at which heat can be removed from extruded filaments by cooling air in the quenching chimney. Higher throughputs usually require higher quench air velocities, but turbulence increases as air velocity increases. Turbulence shakes the hot filaments, causing along-end variations in the denier of the filaments, filaments sticking together and filament breaks.
The prior art teaches that the turbulence of the gas stream in the quenching chamber can be reduced by using a number of screen layers of the same or different mesh lying against each other or in combination with perforated plates. The prior art also teaches that the turbulence can be reduced by using an open-cell foam which is dislcosed in U.S. Pat. Nos. 3,834,847 and 3,619,452. While foam alone can satisfactorily reduce cooling gas turbulence under the conditions disclosed in the two patents, further reduction of turbulence becomes necessary in certain situations where an increase in throughput is desired. It is believed that turbulence of air flow through foam occurs because certain passages through the foam permit higher flow rates than adjacent ones and because the air flow at the exit surface is not directed perpendicularly to the surface from all passages. Flows from two or more adjacent passages may merge beyond the exit surface to form streams of considerably higher velocity or volume than neighboring ones.